Use of a stray electrostatic field for drying leather and the like



Aug. 27, 1940. G. T. HART. JR., ET 1. 2,212,522 USE OF A STRAY ELECTROSTATIC FIELD FOR DRYING LEATHER AND THE LIKE Filed Dec. 1'7, 1937 Tlgil.

Patented 27, 1940 UNITED STATES PATENT OFFICE USE OF A STRAY ELECTROSTATIC FIELD FOR DRYING LEATHER AND THE LIKE George T. Hart, Jr. and Erastus E. Winkley,

Lynn, Mass.,

Flemington,

Application December 17, 1937, Serial No. 180,450

6 Claims.

This invention relates to the utilization of an electrostatic field for the production of heat with-- in an article and is herein illustrated as directed to the drying of moist articles, such as hides, shoe soles and the like.

It is well understood that heat may be produced, as by dielectric hysteresis, in an .article positioned within an electrostatic field set up by currents of high frequency and, previously, this has been accomplished by positioning the article directly withinthe field, between plates or electrodes connected to opposite sides of a suitable source. The energy of such afield, though insufficient to break down the surrounding medium and cause a corona discharge, sets up a heating action within the article itself without heating adjacent metallic or dielectric bodies and has many advantages when applied to the drying of leather articles. If, however, the articles to be treated areof varying shapes and sizes, there is difliculty in securing an efficient relation between the articles and the electrodes and, in many cases, it is found that the drying action does not progress uniformly throughout the article. For example,- when a shoe sole is positioned at right angles to the planes of two parallel electrodes, the central portion of the sole dries before the end portions and if a series of such articles of different lengths is to be treated Sorne of these will dry more quickly than others and will occupy a more advantageous relationship to the electrodes than-others. This matter of relationship refers to the fact that an article may not be brought near enough to an electrode so that sparking occurs between the two. Furthermore, if one article occupies only half the length of the space between the electrodes while another one occupies seventy or eighty per cent, the time of drying of the two articles will be notably difierent, as would be expected. It has been found, however, that the field between two electrodes resembles in many respects the electromagnetic field between the poles of a magnet and that there is a distortion of the direct field between the electrodes when articles are positioned therein resembling the distortion of a magnetic field produced by the insertion of a piece of iron. It is noted further that. aside from the direct field existing at all points in the space between the two electrodes, there is what may be termed a stray or fringe field which bends outwardly from this space. It is possible to utilize this stray field without distorting it as much as is the direct field when articles are positioned therein and to apply it more effectively to articles of various shapes and sizes. This field will be produced by currents of such constants, i. e. frequency, voltage and strength, that there is no breakdown of the air between the electrodes such as is accompanied by a corona discharge and the production of ozone.

Accordingly, one important object of the invention is to provide an improved method of treating articles in an electrostatic field of insufiicient strength to cause a corona discharge wherein the articles to be treated are subjected to only the stray field between electrodes. Preferably and as shown, the articles to .be treated are moved progressively through the stray field so that an integrating action of the field on successive portions of the article is obtained.

Still another object of the invention is to overcome the field distortion and the uneven drying efiect resulting from the use of the direct field between electrode plates by the provision of an improved apparatus.

A feature of the invention resides in an improved apparatus by which the soles of shoes may be treated as to remove themoisture therefrom, and where these,s oles havebeen previously conformedso that theiyare curved sharply at the break of the sole adjacent to the shank portion thereof. In this case, as well as when the attached soles of lasted shoes, especially womens shoes, are to be treated, the effectiveness of the method may be greatly increased by utilizing a form of electrode constructed in accordance with another feature of the invention and in which, as illustrated, the interdigitated bars of two comb-like electrodes are bent or curved into substantial parallelism with the bottom of a typical shoe positioned with its length parallel to the length of the teeth of the electrodes. A conveying apparatus is then provided on which the shoes are so positioned that the breaks in the soles of successive shoes fall along a line beneath and corresponding to the break in the curvature of the teeth of the electrodes. This being done. shoes of diiferent length or of slightly different longitudinal curvature may be treated in the same apparatus with substantially equal efficiency.

These and other features of the invention will be described in the following specification, taken in connection with the accompanying drawing, in which Fig. 1 is a diagrammatic view, showing comblike electrodes positioned in one'plane and being utilized for the treatment of hides positioned on a conveyor traveling in a parallel plane;

Fig. 2 is a vertical section on the line 11-11 of Fig. 1, and

Fig. 3 is a similar section through electrodes which have been curved parallel to the bottom of a lasted shoe carried in inverted position on a conveyor passing beneath said electrodes.

In the arrangement shown in Figs. 1 and 2, hides I0 Which areto be dried have been tacked to boards l2 and these have been positioned on a belt conveyor I4 moving in the direction of the arrow in Fig. 1. Electrodes 20 and 22 mechanically secured to insulators 24 mounted on a frame 26 are connected to opposite sides of a highfrequency oscillator 28. This oscillator, when supplied with powerfrom an alternating current source, not shown, is arranged to deliver electric current of a frequency of from five to'fifty megacycles per second, for example and will be operated with insufficient power to break down the surrounding medium and produce a corona dis charge.

Each of the electrodes 20, 22 is in the form of a comb and the teeth or slats 30 on one electrode are interdigitated with, the teeth 32 on the other electrode and when they are to be utilized for the treatment of flat articles, such as the boarded hides herein illustrated, they are positioned in transverse alignment and, as here shown, in a single plane. It will be understood, then, that the direct field between these electrodes lies befields will each be uniform in their effectiveness along the length of the teeth 30, 32 so that the irregularly shaped hides ill will be uniformly heated regardless of the exact shape'and dimensions of any hide. Each stray field presumably treats a narrow transverse band on the hide which moves through successive stray fields as the con veyor I4 is moved with respect to the electrodes. If desired, the hides may be passed repeatedly through the stray fields and the integrated efiect of the action of the successive fields on the hide will produce a uniform heating therein.

A set of electrodes of this type my have teeth I30, I32 (Fig. 3) bent longitudinally so that the series of teeth form a sort of roof paralleling the curvature of any typical sole 50 attached to a shoe 52 mounted on a last 54. A single shoe will be supported on parallel blades or paddles 56 attached to a conveyor structure 58 moving in a direction normal to the plane of the paper of the drawing. This conveyor structure may have a toe rest 60 and may be of the type shown in-Letters Patent of the United States No. 2, granted September 7, 1937 on the application of H. R. Perry and C. S. Jennings. In each shoe, there will be a substantial break 62 in the lengthwise curvature of the sole and successive shoes on the conveyor will be positioned so that the r breaks lie in substantial alinement beneath the corresponding break 64 in the curvature of the electrode teeth I30, I32.

In carrying out the method, successive articles to be treated will be passed through the stray fields bellying down from the teeth of the electrodes and preferably will be moved in a direction substantially parallel to but outside the series of electrodes without entering the direct field between the electrodes. The treatment will thereupon be applied to bands extending transversely field from said electrodes by moving the articles in a path outside the electrodes without permitting them to enter the space between the electrodes.

2. .The method of treating material which consists in setting up an electrostatic field between electrodes, said field being of a strength insufilcient to break down the surrounding medium and therefore to cause a corona discharge, and cause ing the generation of heat within the material to be treated by subjecting it to that part of the electrostatic field which is external to the space between the electrodes.

3. The method of treating articles which consists insetting up, between two electrodes, an electrostatic field which bulges outside of the space between the electrodes to form a stray field but without causing a corona discharge, and causing a relative movement between said electrodes and an article to cause the stray field to act upon successive portions of the article to set up heat in said successive portions as by dielectric hysteresis.

4. A method of drying shoe soles attached to shoes and having a break at the shank portions which consists in positioning a plurality of shoes side by side so that the breaks in the respective shoes are substantially in alinement, and passing said shoes through the stray electrostatic field produced by a series of curved slat-like electrodes connected alternately to opposite sides of a source of high-frequency electric current.

5. An apparatus for drying shoe soles molded to, substantially the longitudinally curved contour of the bottom of a shoe comprising means for supporting said soles with the tread portions of the soles lying approximately in transverse alinement, and a series of electrodes adapted to be connected to opposite sides of a source of high-frequency electric current, forming between said electrodes an electrostatic field, said electrodes having a longitudinally'curved contour corresponding approximately to the longitudinal contour of the soles and positioned adjacent to said soles to cause the soles to be subjected to the action of the stray field from said electrodes.

6. An apparatus for drying shoe soles attached to shoes and curved lengthwise of the shoes comprising a conveyor for supporting said shoes side by side with the break at the shank portions substantially in alinement, and a series of similarly curved slat-like electrodes adapted to be con nected alternately to opposite sides of a. source of high-frequency electric current, and arranged adjacent to said soles so that the spacing between the soles and the electrodes is substantially uniform throughout a substantial portion of the length of the soles whereby the soles may be passed laterally through the stray fields set up adjacent to the curved electrodes.

GEORGE T. HART, JR. ERASTUS E. WINKLEY.

subjecting the articles to be treated to the stray 

